1. Field of the Invention
The present invention relates to an improved molecular-beam epitaxy system and method, and more particularly to a molecular-beam epitaxy system wherein hydrogen is introduced and employed to change the physical surface properties of the epitaxially grown material and to improve the adsorption property and the quality of the epitaxy.
2. Description of the Prior Art
Molecular-beam epitaxy as a method for epitaxial growth of compound semiconductor films by a process involving the reaction of one or more thermal molecular beams with a crystalline surface under ultra-high vacuum conditions is well known in the art.
A complete discussion of the molecular-beam epitaxy process and the structures for carrying it out is provided by the publication Progress in Solid State Chemistry, Vol. 10 part 3, 1975 in the article "Molecular Beam Epitaxy" by A. Y. Cho and J. R. Arthur at page 157.
Another extensive discussion of the prior art of molecular-beam epitaxy is found in the text Epitaxial Growth Part A of the Materials Science Series. The article "Molecular-Beam Epitaxy" by L. L. Change and R. Ludeke, Section 2.2, pages 37-72 presents a treatise on the theory and techniques employed in the prior art.
The applicants' invention is directed to the use of hydrogen in a molecular-beam epitaxy system to change the physical surface properties of the epitaxially grown material. The use of hydrogen is known in the chemical vapor deposition process as indicated by the publication to R. C. Clark et al, "The Preparation of High Purity Epitaxial In P", Solid State Communications, Vol. 8 (1970), pp. 1125-1128. In a chemical vapor deposition process it is well known that large volumes of hydrogen under high pressure produce an active chemical reaction in the formation of the chemical vapor. For example, in the Clarke et al publication the hydrogen chemically reacts with PCl.sub.3 to produce hydrogen chloride (HCl) and the phosphorous vapor.
In the applicants' invention there is no chemical reaction and the hydrogen is introduced in small volumes under low pressure (ultra-high vacuum) to produce a physical change.
There is no teaching in the prior art relative to the unique use of hydrogen in the molecular-beam evaporation process for epitaxy growth as provided by the present invention, and a review of the prior art will indicate that such use of hydrogen as in the present invention is an unusual and unexpected technique.